CRUSTACEA. 
169 
Post-ABDOMEN. Caudal plate short, sub-quadrangular upon the ventral side, and 
sharply elevated on the anterior edge; sub-pentagonal on the dorsal side, 
elevated in the middle on the posterior half, and produced into a telson 
which is usually about twice as long as the last somite. Articulated to 
the caudal plate are two lateral spines or cercopods, each longer than the 
telson. Each of the three spines is elevated or carinated upon the dorsal 
surface, the telson grooved along the sides, and the cercopods grooved upon 
the ventral surface. 
Surface of the abdomen and caudal spines smooth or finely granulose. 
Dimensions. Although specimens of Echinocaris punctata are not uncommon 
at certain localities, the parts are usually disjointed and entire individuals are 
extremely rare. The most complete specimen observed (pi. xxviii, fig. 3), 
is of average dimensions and measures as follows ; 
Body. Cephalothorax. Abdomen. Post-abdomen. 
Length _ 77 mm. 28 mm. 35 mm. 23 mm. 
Width_ 40 mm. 20 mm. 6 mm. . 
The somites of the abdomen in this specimen have the following lengths; 
First, 4 mm.; second, 4.5 mm.; third, 5 mm.; fourth, 6 mm.; fifth, 6.5 mm.; 
sixth, 9 mm. The largest individual observed in which the parts are in 
conjunction affords the following measurement; 
Body. Cephalothorax. Abdomen. Post-abdomen. 
Length_ 195 mm. 68 mm. 96 mm. 39 mm. 
Width_ 88 mm. 44 mm. _ _ 
A single very large carapace has a length of 90 mm., and the individual to 
which it belonged must have been about 244 mm. or nearly 10 inches in 
length when entire. 
Observations. Specific Diagnosis. The specimen from which the oifiginal 
description of Ceratiocaris ? punctatus, Hall (loc. cit.), was drawn, is a large 
carapace, represented both in the figure given in the Sixteenth ^Report of 
the State Museum, and also in the Illustrations of the Devonian Fossils, with 
a strong node at the posterior extremity of the dorsal line. This node proves 
